Polishing condition control apparatus and polishing condition control method of CMP apparatus

ABSTRACT

To eliminate the unevenness of the remaining film thickness of the wafers, and increase the polishing efficiency, reduce the running cost and enhance the yield. A CMP apparatus  1  is equipped with a polishing recipe preparing means  3  that prepares polishing conditions so that the polishing conditions such as polishing speed, polishing pressure, abrasive and the like for the wafers become optimal, a remaining film thickness forecasting means  4  that forecasts the remaining film thickness of the wafer to be polished under the polishing conditions after polishing, a remaining film thickness measuring apparatus  4  that measures the remaining film thickness of the wafer after the polishing, and a computer  6  that controls the polishing conditions on the basis of the measurement results of the remaining film thickness. Further, the computer  6  includes a calculating unit  11  that calculate the difference between the measured value of the remaining film thickness and the forecasted value thereof, and a polishing condition correcting/changing unit  13  that corrects/changes the polishing conditions so that the calculated difference becomes minimal, and thereby, the correction/change of the polishing conditions is carried out in real time.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polishing condition control apparatusand a polishing condition control method of a CMP apparatus, andparticularly, it relates to a polishing condition control apparatus anda polishing condition control method of a CMP apparatus for optimizingthe polishing condition of a wafer from the measurements result of theremaining film thickness of the wafer.

2. Description of the Related Art

Conventionally, in polishing a wafer by this kind of CMP apparatus, aplaten is rotated by a motor driven, and an abrasive is supplied onto anpolishing pad stuck to the platen, and the wafer is pushed to thepolishing pad while rotating the wafer held by a carrier of thepolishing head, and thereby films to be polished including the oxidefilm, the metal film and the like formed on the wafer surface arepolished.

In the CMP processing, the thickness of remaining film of the wafersurface (hereinafter, referred to as remaining film thickness) ismeasured by use of a remaining film thickness measuring apparatus, andthe wafer is polished so as for the remaining film thickness to becomethe target value. In this case, the remaining film thickness is measuredby the vertical direction displacement of the polishing pad. Inaddition, there are known a method in which the CMP processing isperformed by a simple feedback control of the remaining film thicknessmeasurement, and another method in which the state of the waferpolishing is monitored by a monitor, and the polishing state of thewafers to be polished afterward on the basis of the monitor result isforecasted and polishing is performed (refer to, for example, PatentDocuments 1 to 3).

[Patent Document 1] Japanese Patent No. 308285

[Patent Document 2] Japanese Patent No. 3311864

[Patent Document 3] Japanese Patent Application Laid-Open PublicationNo. 2005-518654

In the conventional CMP apparatus, in the case where the remaining filmthickness of the wafer is measured and polishing is performed, since thevertical direction displacement of the polishing pad is measured as aremaining film thickness, it is difficult to obtain a highly precisemeasurement result. Further, in the case where the CMP processing isperformed by the simple feedback control of the remaining film thicknessmeasurement, it is not possible to obtain a high remaining filmthickness measurement result stably, and consequently, the method doesnot cope with ultrafine and highly integrated wafers sufficiently.

On the other hand, in the case where the state of the wafer polishing ismonitored by a monitor, and the polishing state of the wafers to bepolished afterward is forecasted, the polishing conditions differ withthe respective modules of the apparatus, that is, respective rotatingaxes (hereinafter referred to as polishing axes), and respectiveplatens, and as a result, the film thickness of wafers after thepolishing process is apt to be uneven among the modules.

As mentioned, according to the conventional art, it is difficult toprecisely measure the remaining film thickness of the wafers, and sinceunevenness in the remaining film thickness occurs among the modules,excessive polishing and insufficient polishing easily take place, andpolishing efficiency of the wafer declines. Defects occur in wafersafter the polishing, and the yield decreases. Furthermore, expendablesupplies such as abrasives are wasted more than necessary, andaccordingly the running cost of the expendable supplies increases, andthese have been problems in the conventional art.

SUMMARY OF THE INVENTION

Therefore, there has been a technological subject to eliminate theunevenness of the remaining film thickness of the wafers, and increasethe polishing efficiency, reduce the running cost and enhance the yield,and accordingly, the object of the present invention is to solve theproblems.

The present invention has been made to achieve the object, and accordingto a first aspect of the present invention, there is provided apolishing condition control apparatus of the CMP apparatus that polishesthe film to be polished formed on the wafer surface, and the polishingcondition control apparatus includes, a polishing recipe preparing meansthat prepares polishing conditions so that the polishing conditions suchas polishing speed, polishing pressure, and an abrasive and the like forthe wafer become optimal, a remaining film thickness forecasting meansthat forecasts the remaining film thickness of the wafer to be polishedunder the polishing conditions after polishing, a remaining filmthickness measuring apparatus that measures the remaining film thicknessof the wafer after the polishing, and a computer that controls themeasurement results of the remaining film thickness and the polishingconditions, and further the computer includes a calculating unit thatcalculate the difference between the measured value of the remainingfilm thickness and the forecasted value thereof, and a polishingcondition correcting/changing unit that corrects/changes the polishingconditions so that the calculated difference becomes minimal, andthereby, the correction/change of the polishing conditions is carriedout in real time.

According to this structure, the polishing conditions are prepared bythe polishing recipe preparing means so that the polishing conditionssuch as polishing speed, polishing pressure, abrasives and the likebecome optimal, further, the remaining film thickness of the waferpolished under the optimal polishing conditions after the polishing isforecasted by the remaining film thickness forecasting means.

And, after wafer is polished under the optimal polishing conditions, theremaining film thickness of the wafer surface by the remaining filmthickness measuring apparatus. In the next time and after that, thedifference between the measured value of the remaining film thicknessand the forecasted value thereof is calculated by the calculating unitof the computer, and the polishing conditions are corrected/changed bythe polishing condition correcting/changing unit in real time so thatthe calculated difference becomes minimal. Thus, wafers are alwayspolished under the optimal polishing conditions, and the remaining filmthickness of the wafers are processed into the target value.

According to a second aspect of the present invention, there is provideda polishing condition control apparatus of a CMP apparatus according tothe first aspect of the invention, wherein the polishing recipepreparing means prepares the optimal polishing conditions for eachpolishing step of the wafer, each polishing shaft of the CMP apparatus,each platen, or each combination of the polishing shaft and the platen.

According to this structure, the optimal polishing conditions areprepared for each polishing step of the wafer, each polishing shaftcorresponding to a rotating shaft of the polishing head, each platen, oreach combination of the polishing shaft and the platen. Therefore, thewafers are polished under the optimal polishing conditions according toeach individual polishing step, polishing shaft, or platen.

According to a third aspect of the present invention, there is provideda polishing condition control apparatus of a CMP apparatus according tothe first or second aspect of the invention, wherein the polishingrecipe preparing means prepares the optimal polishing conditions on thebasis of data of an approximate expression prepared from past polishinghistory and a polishing model that the CMP apparatus itself storesbeforehand.

According to this structure, since the optimal polishing condition isprepared on the basis of the data of the approximate expression preparedfrom past polishing history, and the polishing model that the CMPapparatus itself stores beforehand, the polishing conditions thatreflect the data of the past polishing history and the polishing modelpeculiar to the apparatus are prepared. The polishing model is a modelshowing the relations between of polishing parameters such as thepolishing pressure and the polishing time and the like and the polishingquantity that are made into fixed quantities and numerical values.

According to a fourth aspect of the present invention, there is provideda polishing condition control apparatus of a CMP apparatus according tothe first aspect of the invention, wherein the remaining film thicknessforecasting means forecasts the remaining film thickness of the wafer onthe basis of the approximate expression prepared from past polishinghistory.

According to this structure, the remaining film thickness of the waferis forecasted on the basis of the approximate expression prepared fromthe past polishing history, and accordingly, the data of the polishinghistory is reflected to the forecasted value of remaining film thicknessof the wafer.

According to a fifth aspect of the present invention, there is provideda polishing condition control apparatus of a CMP apparatus according tothe first aspect of the invention, wherein the computer has a monitoringunit that displays the difference between the measured value of thepolishing time and the forecasted value thereof, and, polishing statesof the wafers and the like.

According to this structure, since the difference between the measuredvalue of the polishing time and the forecasted value thereof, andpolishing states of the wafers and the like are monitored by themonitoring unit, changing data and polishing condition are grasped inreal time.

According to a sixth aspect of the present invention, there is provideda polishing condition control apparatus of a CMP apparatus according tothe first or fifth aspect of the invention, wherein the computerincludes a polishing state judging unit that outputs an attentionsignal, an alarm signal and/or a polishing stop signal, when thecalculated difference exceeds a predetermined value.

According to this structure, when the calculated difference exceeds thespecified value, the attention signal, the alarm signal and/or thepolishing stop signal are output. Accordingly, when the polishing stategets erroneous, the effect to that is automatically notified, and at anemergency, the polishing process is stopped immediately.

According to a seventh aspect of the present invention, there isprovided a polishing condition control apparatus of a CMP apparatusaccording to the first aspect of the invention, wherein the polishingcondition correcting/changing unit corrects/changes the polishingconditions for each polishing step of the wafer, each polishing shaft ofthe CMP apparatus, each platen, or each combination of the polishingshaft and the platen.

According to this structure, the correction/change of the polishingconditions is performed independently for each polishing step, eachpolishing shaft, each platen, or each combination of the polishing shaftand the platen. Therefore, the polishing conditions arecorrected/changed to the optimal polishing conditions for each polishingstep, and further, the optimal polishing conditions arecorrected/changed in the same manner among the polishing shafts, theplatens, or, the combinations of the polishing shaft and the platen.

According to an eighth aspect of the present invention, there isprovided a polishing condition control method of a CMP apparatus thatpolishes a film to be polished formed on the wafer surface, and thepolishing condition control method includes, a polishing recipepreparing step of preparing polishing conditions so that the polishingconditions such as polishing speed, polishing pressure, and an abrasiveand the like for the wafer become optimal, a remaining film thicknessforecasting step of forecasting the remaining film thickness of thewafer to be polished under the polishing conditions after polishing, aremaining film thickness measuring step of measuring the remaining filmthickness of the wafer after the polishing, and a calculating step ofcalculating the difference between the measured value of the remainingfilm thickness and the forecasted value thereof, and a polishingcondition correcting/changing step of correcting/changing the polishingconditions so that the calculated difference becomes minimal, andthereby, the correction/change of the polishing conditions is carriedout in real time.

According to this method, the polishing conditions are so prepared thatthe polishing conditions such as polishing speed, polishing pressure,abrasives and the like become optimal, further, the remaining filmthickness of the wafer to be polished under the optimal polishingconditions after polishing is forecasted. And, after the wafer ispolished under the optimal polishing conditions, the remaining filmthickness of the wafer surface is measured. In the next time and afterthat, the difference between the measured value of the remaining filmthickness and the forecasted value thereof is calculated, subsequently,the polishing conditions are corrected/changed in real time so that thedifference becomes minimal. Thus, wafers are always processed under theoptimal polishing conditions, and the remaining film thickness of thewafers is processed smoothly into the target film thickness.

According to the first aspect of the present invention, the polishingconditions such as the polishing speed (polishing time), and the flowquantity of abrasives and the like can be always maintained optimally,and accordingly, it is possible to eliminate the unevenness in theremaining film thickness of the wafers by eliminating the excessivepolishing and insufficient polishing, and improve the polishingefficiency, and reduce running costs (wastes of abrasives and the like).In addition, since the occurrence of defective products can beprevented, and the yield can be improved.

According to the second aspect of the present invention, the optimalpolishing conditions can be prepared according to individual polishingstep, polishing shaft or platen, and accordingly, in addition to theeffect of the first aspect, it is possible to polish the remaining filmthickness of the wafers into the target value more efficiently.

According to the third aspect of the present invention, since it ispossible to obtain the polishing conditions that reflect the data of thepast polishing history and the polishing model peculiar to theapparatus, in addition to the effect of the first or second aspect, itis possible to polish the remaining film thickness of the wafer into thetarget value more precisely.

According to the fourth aspect of the present invention, since theremaining film thickness of the wafer is forecasted on the basis of thedata of the past polishing history, and accordingly, in addition to theeffect of the first aspect, it has a merit to increase the reliabilityof the forecasted value of the remaining film thickness.

According to the fifth aspect of the present invention, since it ispossible to grasp the changing result data and polishing states in realtime, in addition to the effect of the first aspect, it is possible tocheck whether the polishing process of the wafers goes well.

According to the sixth aspect of the present invention, since when thepolishing state gets erroneous, the effect to that is automaticallynotified, and at an emergency, the polishing process is stoppedimmediately, in addition to the effect of the first or fifth aspect, itis possible to prevent the wafer from being polished and processed in anerroneous state.

According to the seventh aspect of the present invention, since theoptimal polishing conditions can be corrected/changed independently foreach polishing step, each polishing shaft, each platen, or eachcombination of the polishing shaft and the platen, in addition to theeffect of the first aspect, it is possible to eliminate the unevennessof the remaining film thickness of wafers among the polishing steps, thepolishing shafts and/or the platens more efficiently.

According to the eighth aspect of the present invention, the polishingconditions such as the polishing speed (polishing time), and the flowquantity of abrasives and the like are always maintained, andaccordingly, it is possible to improve the polishing precision of theremaining film thickness of the wafers, and the unevenness of the filmthickness of the wafers can be eliminated, and further the high runningcosts (the wastes of abrasives) can be reduced. Furthermore, since theoccurrence of defective products can be reduced, it is possible toimprove the yield of the wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a polishing condition controlapparatus of a CMP apparatus according to an embodiment of the presentinvention;

FIG. 2 is a perspective view showing a polishing unit according to anembodiment;

FIG. 3 is a flow chart for explaining the procedure of a polishingcondition control according to an embodiment;

FIG. 4 are graphs showing the relation between the number of alreadypolished sheets and the remaining film quantity, and 4A is a graph forexplaining the permissible range of the remaining film quantity, and 4Bis a graph for explaining the real polishing time and the forecastedtime; and

FIG. 5 are graphs for explaining the characteristics of a polishingmodel according to an embodiment, and 5A is a graph for explaining acase where the remaining film quantity increases with time with thepolishing pressure as its parameter, and 5B is a graph for explaining acase where the remaining film quantity decreases with time with thepolishing pressure as its parameter, and 5C is a graph showing therelation between the remaining film quantity and the polishing time whenthe polishing speed changes.

DESCRIPTION OF PREFERRED EMBODIMENTS

In order to achieve the object to eliminate the unevenness of theremaining film thickness of the wafers, and, increase the polishingefficiency, reduce the running cost and enhance the yield, the presentinvention is embodied by that in a CMP apparatus that polishes a film tobe polished formed on the wafer surface, a polishing recipe preparingmeans that prepares polishing conditions so that the polishingconditions such as polishing speed, polishing pressure, and an abrasiveand the like for the wafer become optimal, a remaining film thicknessforecasting means that forecasts the remaining film thickness of thewafer to be polished under the polishing conditions after polishing, aremaining film thickness measuring apparatus that measures the remainingfilm thickness of the wafer after the polishing, and a computer thatcontrols the measurement results of the remaining film thickness and thepolishing conditions, are arranged, and further, the computer includes acalculating unit that calculate the difference between the measuredvalue of the remaining film thickness and the forecasted value thereof,and a polishing condition correcting/changing unit that corrects/changesthe polishing conditions so that the calculated difference becomesminimal, and thereby, the correction/change of the polishing conditionsis carried out in real time.

Hereinafter, an embodiment according to the present invention isexplained with reference to FIG. 1 through FIG. 5. The presentembodiment is structured so that the optimal polishing conditions areprepared, and the remaining film thickness of the wafers is forecasted,and the wafers are processes by CMP, and thereafter, the remaining filmthickness of the wafers after polished is measured for each module, andthe difference between the measured value of the remaining filmthickness and the forecasted value thereof are compared and thereby thedifference thereof is obtained, and the polishing conditions arecorrected/changed in real time as much as possible so that thedifference becomes minimal.

The data of the polishing history including the polishing time and thepolishing quantity and the like acquired by the polishing process ofwafers are controlled for each polishing shaft and/or each platen, andthe data is used in preparing the polishing conditions. The forecastedvalue of the remaining film thickness may be calculated on the basis ofthe approximate expression prepared from the past polishing historydata. Furthermore, the whole or part of the plural polishing conditions,detection results and polishing states may always be monitoredoptionally and selectively by the monitoring unit.

As shown in FIG. 1, a CMP apparatus 1 is structured of a remaining filmthickness measuring apparatus 2, a polishing recipe preparing means 3, aremaining film thickness forecasting means 4, a polishing unit 5 and acomputer 6 and the like. The remaining film thickness measuringapparatus 2 measures the remaining film thickness of the wafers afterthe polishing. And, the polishing recipe preparing means 3 prepares thepolishing conditions so that the polishing conditions such as thepolishing speed, the polishing pressure, and abrasives and the likebecome optimal.

The polishing recipe preparing means 3 refers to the past polishinghistory for each polishing step, or, each polishing shaft, each platen,or each combination of the polishing shaft and the platen, and therebyprepares the optimal polishing conditions.

Further, the polishing recipe preparing means 3 may prepare the optimalpolishing conditions on the basis of one or both of the data on thebasis of the approximate expression prepared from the past abrasionhistory, and the data of the polishing model which the CMP apparatus 1has stored beforehand.

For example, FIG. 5A is a graph of a polishing model showing therelations between the polishing time and the polishing quantity at eachpolishing pressure that are made into fixed quantities and numericalvalues. FIG. 5B is a graph of a polishing model showing the relationsbetween the polishing time and the polishing quantity at each polishingpressure that are made into fixed quantities and numerical values, onthe basis of FIG. 5A, in the case where the film thickness beforepolishing is 280 nm. By these polishing models, the forecasted polishingquantity is calculated.

In this case, the latest data of the polishing history may be weightedand used.

The remaining film thickness forecasting means 4 forecasts the remainingfilm thickness of the wafer after the polishing to be polished under thepolishing conditions. It can forecast the remaining film thickness ofthe wafer on the basis of the approximate expression prepared from thepast polishing history. Meanwhile, the function of the remaining filmthickness forecasting means 4 may also be performed by the polishingrecipe preparing means 3.

In addition, the polishing unit 5 is the main body unit of a CMPapparatus that polishes wafers, and as shown in FIG. 2, it is structuredso as to rotate a rotating shaft 8A of a platen 8 by a motor 7, andsupply an abrasive (not illustrated) onto a polishing pad 9 attached tothe platen 8, and drive to rotate a polishing shaft 10A of a polishinghead 10 and rotate a wafer held on the polishing head 10, and push thewafer onto the polishing pad 9, and thereby polish the film to bepolished of the wafer surface.

The computer 6 performs the control of the polishing condition on thebasis of the measurement result of the remaining film thickness. Thiscomputer 6 includes a calculating unit 11, a memory unit 12, a polishingcondition correcting/changing unit 13, a monitoring unit 14, a polishingstate judging unit 15 and an apparatus control unit 16 and the like. Thecalculating unit 11 calculates the difference between the measured valueof the remaining film thickness and the forecasted value thereof. Inaddition, the memory unit 12 memorizes the data of control state of thepolishing conditions and others on the basis of the measurement resultof the remaining film thickness.

Further, the polishing condition correcting/changing unit 13corrects/changes the polishing conditions so that, when the calculateddifference is a specified value or, the difference becomes minimal. Inmore addition, the monitor unit 14 displays difference between themeasured value of the remaining film thickness and the forecasted valuethereof, as well as the polishing state of the wafer. In addition, thepolishing state judging unit 15 outputs an attention signal, an alarmsignal and/or a polishing stop signal, when the calculated difference isthe specified value or. Furthermore, the apparatus control unit 16 has afunction to control the actions of respective portions of the CMPapparatus mainly on the basis of various kinds of order signals and thelike.

The polishing condition control method according to the presentembodiment makes the control on the basis of the measurement result ofthe remaining film thickness of the wafers and the forecast resultbefore the polishing. The forecast result is the value set by obtainingan appropriate polishing time of the wafers.

In addition, when the polishing end point detection (not illustrated) isemployed, in addition to the measurement result and the forecast resultbefore polishing, the control of the end point detection result is alsocarried out. Meanwhile, the detection principle of the polishing endpoint detection means is not limited in particular, and, for example, amethod to detect the torque fluctuation of the drive motor of thepolishing head 10 or the platen 8, or a method to optically detect theremaining film thickness, and a method to use an eddy current and thelike may be employed.

The polishing condition control apparatus 11 measure films to bepolished including the metal film, oxide film and the like formed on thewafer surface after polishing for each module, that is, for eachpolishing shaft 10A, each platen 8, or, each combination of thepolishing shaft 10A and the platen 8, and compares the measured valuewith the forecasted value, and corrects/changes the polishing conditionsin real time as much as possible so that the difference becomes minimal.

As the polishing conditions, there are, for example, the polishing time,the polishing pressures (wafer pressure, zone pressure), the polishingspeed (rotation speed of the platen 8 or the polishing shaft 10A), thepolishing temperature of the wafer (the temperature of the polishinghead, the temperature of the platen 8), the air flow quantity in thepolishing head 10, and the kinds, components and flow quantity ofabrasives, the like.

In the evaluation of the results of the measured remaining filmthickness, a modulus difference or a deviation (a deviation of theremaining film thickness to the average remaining film thickness)between the measured value and the forecasted value is adopted, and theevaluation is carried out for each polishing step, or each polishingshaft 10A, each platen 8, or each combination of the polishing shaft 10Aand the platen 8.

Hereinafter, an example of the procedure of the polishing conditioncontrol according to the present embodiment is explained in detail withreference to the flow chart in FIG. 3. First, the optimal polishingconditions are prepared by the polishing condition preparing unit (stepS1). In this case, in consideration of useful information pieces aboutthe polishing conditions to be obtained from wafer processing factoriesand bar code leaders, the polishing conditions are prepared for eachpolishing step.

In the preparation of the optimal polishing conditions, the polishingconditions are determined on the basis of a calculating expression. Inthis case, by many polishing history information, an approximateexpression of the relations between the polishing conditions such as thepolishing time, the polishing quantity, and on the basis of the resultcalculated by inserting concrete data into this approximate expression,the optimal polishing conditions to the wafers (objectives to bepolished) W at the next time and after that are determined and adopted.FIG. 4A is a graph showing the relation between the number of alreadypolished wafers and the remaining film quantity. In the figure, on thebasis of this increase-decrease rate of the remaining film quantity tothe latest i-th (i being an integer n of 1 or higher) wafer, theinclination in the graph, that is, the degree of changes of theremaining film quantity to the number of the already polished wafers isobtained. Then, on the basis of the degree of changes of the remainingfilm quantity, the remaining film quantity of the next (i+1)-th wafer isobtained, and the obtained remaining film quantity is assigned to theapproximate expression, and the optimal polishing conditions aredetermined and adopted.

FIG. 4B is a graph showing the relations between the number of alreadypolished wafers and the remaining film quantity. On the basis of thedegree of the change of this remaining film quantity, an approximateexpression using a multinomial expression approximation curve isprepared, and the remaining film quantity of the next (i+1)-th wafer isobtained, and the obtained remaining film quantity is assigned to theEDP time, and the forecasted value is obtained by extrapolation. On thebasis of the forecasted value, the remaining film quantity of the(i+1)-th wafer is obtained, and the obtained remaining film quantity isassigned to the approximate expression, and thereby, the optimalpolishing conditions are determined and adopted.

The remaining film thickness after the polishing of the wafer polishedunder the polishing conditions at the next time and after that isforecasted by the remaining film thickness forecasting means 4 (stepS2). The forecast of this remaining film thickness is completed beforethe remaining film thickness of the wafer is measured by the remainingfilm thickness measuring apparatus at step S4. Then, at step S3, the CMPprocessing is started. The polishing data acquired by the CMP processingis controlled for each polishing shaft 10A and/or each platen 8, or eachpolishing step.

As the polishing data, the data of the polishing time, the remainingfilm quantity of each polishing process type, the EPD time, the use timeand the number of used pieces of expendable supplies of the polishingpad 9 and the polishing head 10, and the temperature of the polishingpad 9, the temperature of the polishing head 10 and the like areincluded. These polishing data are memorized and controlled in thememory unit 12 as the past polishing history, and are used as usefuldata pieces when the optimal polishing recipes are prepared (step S4).

For example, among the polishing data, the polishing time, the remainingfilm quantity of each polishing process type, and the EPD time arecontrolled for each polishing step (for each polishing process type),and for each platen 8. In addition, the use time and the number of usedpieces of expendable supplies such as abrasives and the like arecontrolled for each polishing shaft 10A and/or each platen 8. Further,the use time or the number of used pieces of the polishing pad 9, andthe dressers is controlled for each platen 8, and the use time or thenumber of used pieces of the retainers for wafers and the polishing head10 is controlled for each polishing shaft 10A. In the presentembodiment, the polishing temperature of the wafer is also controlledfor each polishing shaft 10A and/or each platen 8. For example, thetemperature of the polishing pad 9 is controlled for each platen 8, andthe temperature of the polishing head 10 is controlled for eachpolishing shaft 10A.

Thereafter, the remaining film thickness of the wafer is measured by theremaining film thickness measuring apparatus at step S5. In this case, ametal film remaining film thickness measuring apparatus or an oxide filmremaining film thickness measuring apparatus is employed according tothe kind of the film to be polished, and the measurement principle ofthe remaining film thickness measuring apparatus may be any of anoptical method, an electric capacity method, an X-rays method, an eddycurrent method and the like.

At the next time and after that, the progress states of the CMPprocessing, that is, the change states of the wafer polished surface andthe polishing temperature and the like are displayed in real time on themonitor unit 6 and are confirmed. In the present embodiment, aconfirmation screen is divided into three ways and confirmed. In theconfirmation screen 1, the result of calculating the difference betweenthe forecasted value of the remaining film thickness and the measuredvalue thereof by the calculating unit 11 is confirmed.

Further, in the confirmation screen 2, the use time and the number ofsheets used for polishing of the expendable supplies such as abrasives,polishing pads and the like are monitored for each apparatus (for eachpolishing shaft 10A or each platen 8), and it is confirmed whether theuse time and the number of sheets used for polishing are away fromspecified values preset for the each apparatus.

Furthermore, in the confirmation screen 3, the polishing temperature ofthe wafer measured by the temperature sensor, that is, the temperatureof the polishing pad or the temperature of the polishing head aremonitored, and it is confirmed whether the measuring temperature areaway from specified values preset for the apparatus.

At the next time and after that, on the basis of the gap value betweenthe result value and the forecasted value, and the unevenness of theresult value, it is evaluated and judged whether the polishing is normalor abnormal (step S7). This evaluation is judged for each polishingstep, and each polishing shaft 10A and/or each platen 8 by the polishingstate judging unit 15. In the present embodiment, this judgment isevaluated into three states of “Normal state”, “Attention state” and“Warning state”.

That is, according to whether the gap value between the result value andthe measured value, or the unevenness value of result values is largerthan the predetermined permissible value or a warning value, theevaluation is made into three stages, and, a signal corresponding to theevaluation is output to the outside or the respective units of theapparatus. For example, in the case where the value is below thepermissible value, it is judged as a “Normal state”, and the polishingprocess of the wafers at the next time and after that is continued as itis.

In addition, in the case where the value is the permissible value, andbelow the warming value, it is judged as an “Attention state”, and anattention signal (alarm) is given for attention to the operator.Furthermore, in the case where the value is the warning value, it isjudged as a “Warning state”, and a warning signal (alarm) is given forattention to the operator, and also a polishing stop signal is outputand the polishing process is stopped immediately. In addition, in thecase when the gap value between the result value and the forecastedvalue exceeds the predetermined range, the approximate expressions andthe like are changed. Further, the evaluation may be made by acombination of the evaluation methods of the “Attention state” and“Warning state”.

As explained, according to the present embodiment, the polishingconditions such as the polishing speed, the polishing pressure, theabrasives, and the like for the wafers are prepared by the polishingrecipe preparing means 3 so as to become optimal, and the polishingconditions are corrected/changed in real time by the polishing conditioncorrecting/changing unit 13 so that the difference between the measuredvalue of the remaining film thickness of the wafers after polishing andthe forecasted value thereof becomes minimal.

For example, as shown in FIG. 5C, in the case when the polishing speedis low by 30%, the target remaining film quantity is calculated at step10. In addition, after the approximate expression is obtained when thepolishing speed is low by 30%, at steps 11 and 12, the polishing time isexpanded until the target polishing speed is obtained while thepolishing speed is low by 30%.

Meanwhile, since the film thickness measurement of the wafers W iscarried out after the wafers W are washed, the polishing conditionsafter the correction/change is not always reflected to the wafer W thatis polished after the first wafer W that is measured, and they may bereflected to the second wafer W and wafer after that to be polished.

Therefore, since the polishing conditions such as the polishing speed,the polishing time, the flow quantity of abrasives and the like can bealways maintained optimally, the remaining film thickness of the wafersis polished precisely into the target value, and accordingly, it ispossible to eliminate the unevenness of the remaining film thickness ofthe wafers, and improve the polishing efficiency. In addition, the usetime of the expendable supplies such as the polishing pads 9, thepolishing heads 10, abrasives and the like is shortened to a necessaryminimum, and consequently, the running cost is reduced by reducing thewaste of expendable supplies. Furthermore, the occurrence of defectiveproducts is decreased, and consequently, it is possible to enhance theyield substantially.

Further, the past polishing histories are referred to for each polishingstep of the wafers, or, each polishing shaft 10A or, each platen 8, or,each combination of the polishing shaft 10A and the platen 8, andthereby the optimal polishing conditions are prepared. And consequently,it is possible to polish the wafers under the optimal polishingconditions individually set for each polishing step, each polishingshaft 10A or each platen 8, and accordingly it is possible to polish theremaining film thickness of the wafers into the target value furthermore efficiently.

Furthermore, in the case when the data of the latest polishing historyof high information value is weighted, since wafers can be polishedunder the polishing conditions in which importance is put on the latestraw data, the polishing efficiency of the wafers improves further more.

Moreover, in the preparation of the polishing conditions, theapproximate expression prepared from the past polishing history, and thedata of the polishing model that the apparatus itself already stores areused, the wafers can be polished under the polishing conditionsreflecting the data of the past polishing history and the polishingmodel peculiar to the apparatus, and consequently, it is possible topolish the remaining film thickness of the wafers efficiently andprecisely.

Still further, since the remaining film thickness of the wafers isforecasted on the basis of the approximate expression prepared from thepast polishing history, it is possible to obtain a highly reliableforecasted value.

Furthermore, since the difference between the measured value of thepolishing time and the forecasted value thereof, and the polishingstates of the wafers can be monitored and grasped on the screen of themonitoring unit 14 in real time, it is possible to easily confirm thepolishing states of the wafers during the polishing, and always maintainthe polishing conditions according to the specifications of the wafersand the polishing environment.

Moreover, when the calculated difference value is of the permissiblevalue or the attention signal is automatically output from the polishingstate judging unit 15, and, when the calculated difference value is ofthe warning value or the warning signal and the polishing stop signalare automatically output, and accordingly, even an erroneous polishingstate occurs, such a state can be coped with immediately andappropriately.

In the present embodiment, the correction/change of the polishingconditions are carried out independently for each polishing step of thewafers, each polishing shaft 10A, each platen 8, or each combination ofthe polishing shaft 10A and the platen 8. Accordingly, it is possible toobtain the optimal polishing conditions according to each polishingstep, and to obtain the optimal polishing conditions according to eachpolishing shaft 10A, each platen 8, or each combination of the polishingshaft 10A and the platen 8. And consequently, it is possible toeliminate the unevenness of the remaining film thickness of the wafersamong plural polishing steps, polishing shafts 10A and/or platens 8.

The present invention can be variously modified within the scope of thepresent invention, and it goes without saying that the present inventioncomes to the modified structure.

DESCRIPTION OF REFERENCE NUMERALS

-   1 CMP apparatus-   2 Remaining film thickness measuring apparatus-   3 Polishing recipe preparing means-   4 Remaining film thickness forecasting means-   5 Polishing unit-   6 Computer (control means)-   8 Platen-   10 Polishing head-   11 Calculating unit-   12 Memory unit-   13 Polishing condition correcting/changing unit-   14 Monitoring unit-   15 Polishing state judging unit

1. A polishing condition control apparatus of a CMP apparatus thatpolishes a film to be polished formed on the wafer surface comprising: apolishing recipe preparing means that prepares polishing conditions sothat the polishing conditions such as polishing speed, polishingpressure, and an abrasive and the like for the wafer become optimal; aremaining film thickness forecasting means that forecasts the remainingfilm thickness of the wafer to be polished under the polishingconditions after polishing; a remaining film thickness measuringapparatus that measures the remaining film thickness of the wafer afterthe polishing; and a computer that controls the measurement results ofthe remaining film thickness and the polishing conditions, the computerfurther includes a calculating unit that calculate the differencebetween the measured value of the remaining film thickness and theforecasted value thereof, and a polishing condition correcting/changingunit that corrects/changes the polishing conditions so that thecalculated difference becomes minimal, wherein the correction/change ofthe polishing conditions are carried out in real time.
 2. The polishingcondition control apparatus of a CMP apparatus according to claim 1,wherein the polishing recipe preparing means prepares the optimalpolishing conditions for each polishing step of the wafer, eachpolishing shaft of the CMP apparatus, each platen, or each combinationof the polishing shaft and the platen.
 3. The polishing conditioncontrol apparatus of a CMP apparatus according to claim 1 or 2, whereinthe polishing recipe preparing means prepares the optimal polishingconditions on the basis of data of an approximate expression preparedfrom past polishing history and/or a polishing model that the CMPapparatus itself stores beforehand.
 4. The polishing condition controlapparatus of a CMP apparatus according to claim 1, wherein the remainingfilm thickness forecasting means forecasts the remaining film thicknessof the wafer on the basis of the approximate expression prepared frompast polishing history.
 5. The polishing condition control apparatus ofa CMP apparatus according to claim 1, wherein the computer has amonitoring unit that displays the difference between the measured valueof the remaining film thickness and the forecasted value thereof, andpolishing states of the wafers and the like.
 6. The polishing conditioncontrol apparatus of a CMP apparatus according to claim 1 or 5, whereinthe computer includes a polishing state judging unit that outputs anattention signal, an alarm signal and/or a polishing stop signal, whenthe calculated difference exceeds a specified value.
 7. The polishingcondition control apparatus of a CMP apparatus according to claim 1,wherein the polishing condition correcting/changing unitcorrects/changes the polishing conditions for each polishing step of thewafer, each polishing shaft of the CMP apparatus, each platen, or eachcombination of the polishing shaft and the platen.
 8. A polishingcondition control method of a CMP apparatus that polishes a film to bepolished formed on the wafer surface comprising: a polishing recipepreparing step that prepares polishing conditions so that the polishingconditions such as polishing speed, polishing pressure, and an abrasiveand the like for the wafer become optimal; a remaining film thicknessforecasting step that forecasts the remaining film thickness of thewafer to be polished under the polishing conditions after polishing; aremaining film thickness measuring step that measures the remaining filmthickness of the wafer after the polishing; a calculating step thatcalculates the difference between the measured value of the remainingfilm thickness and the forecasted value thereof; and a polishingcondition correcting/changing step that corrects/changes the polishingconditions so that the calculated difference becomes minimal, whereinthe correction/change of the polishing conditions are carried out inreal time.